Thermoelectric modules are based on the Peltier effect, which states that a DC current applied across two dissimilar materials causes a temperature differential. A typical thermoelectric module comprises two ceramic wafers with a series of P- and N-doped thermoelectric elements sandwiched between them. One P- and one N-type thermoelectric element make up a thermoelectric couple. Thermoelectric couples are connected electrically in series and thermally in parallel. A thermoelectric module can contain one to several hundred couples. Its performance is proportional to the electrical current and the number of thermoelectric couples. Thermoelectric modules are used in device cooling, power generation, and temperature stabilization.
Conventionally, thermoelectric modules are produced by slicing ingot thermoelectric material into bulk thermoelectric elements and bonding them onto electrodes through soldering or like techniques. Ingot thermoelectric materials are produced using high temperature alloying, powder sintering, poly-crystallization zone melting, amorphous production as well as other techniques known to those skilled in the art. However, conventional production of thermoelectric modules involves numerous problems. For example, the process is complicated. High temperature and long processing times are needed to produce ingot thermoelectric materials. Thus the productivity is low and the cost is high. In addition, process automation is difficult since the thermoelectric elements are produced by slicing only one at a time. This too leads to high production costs. Finally, assembly of thermoelectric modules requires placement and attachment of the individual, and sometimes very small, thermoelectric elements.
An additional problem encountered with conventional production of thermoelectric modules is the notably lower yield of thermoelectric elements when the thickness of the thermoelectric elements is less than 1.5 mm. This is due to the difficulty in cutting ingot thermoelectric materials. Miniaturization of thermoelectric elements is very difficult. As a result, the number of thermoelectric couples that can be fabricated in a thermoelectric module is limited. Thus, the efficiency of the thermoelectric modules is rather low. In summary, it is very difficult to produce compact, high performance thermoelectric modules using conventional methods.
Accordingly, new processing methods are thus needed for cost-effectively producing compact thermoelectric modules with a multitude of thermoelectric couples.